One configuration for a supplemental inflatable restraint system in an automotive vehicle may comprise the presence of multiple supplemental inflatable restraint devices in a single vehicle, for example a driver's side air bag and a passenger's side air bag. Each supplemental inflatable restraint device is initiated by its own independent electrical circuit, and each circuit includes an inertia switch which is devoted exclusively to the corresponding supplemental inflatable restraint device.
While the inertia switches that are exclusive to each supplemental inflatable restraint device must comply with certain engineering specifications, there are certain manufacturing considerations which in the course of mass production of such switches may result in some switches having slightly different, but tolerable, response characteristics from those of other switches. In any given automotive vehicle, such differences may affect the precision with which simultaneous circuit initiations will occur in the event of a deceleration that calls for deployment of the supplemental inflatable restraint devices.
One way of attaining a greater degree of precision in simultaneously signalling multiple supplemental inflatable restraint devices by electrically exclusive switches is to have the switches operated by a single inertial mass instead of by their own individual masses. It can be especially advantageous for the required inertial switch functions to be embodied in a single inertia switch assembly that independently serves plural supplemental inflatable restraint devices. Since the response characteristic of an inertial switch to deceleration is desirably determined for the mostpart by the nature of the inertial mass, as distinguished from the nature of the electrical portion of the switch, the avoidance of duplication of inertial masses and related structure can result in an overall cost savings. Likewise, if one inertia switch assembly can serve plural supplemental inflatable restraint devices, savings on installation time and in the cost of wiring harnesses and electrical connectors that place the inertia switches in the supplemental inflatable restraint electrical circuits may also be realized.
In embodying multiple sets of switch contacts in an inertial switch that has only a single inertial actuator, it is important to assure the mutual isolation (i.e., electrical independency) of the individual sets of contacts and to also provide for the sets to be related in assembly such that each will respond in exactly the same manner upon actuation by the common inertial mass. Furthermore, it may be necessary for the inertial mass to be comparatively small and to execute only a small amount of travel to operate the sets of contacts. Consideration of these factors means that each set of contacts may be required to operate in response to a comparatively small actuating force. In an automotive vehicle it is also necessary that the inertial switch be able to withstand reasonable levels of vibration without giving false indications. Yet, when called upon to be actuated, the sets of contacts must be able to carry a relatively high amount of current even though the duration of that current may be relatively small. For example, a set of contacts may be required to meet a specification of carrying sixteen amps of current for a duration of thirty milliseconds upon actuation. The switch must also be able to withstand a certain amount of overtravel of the inertial mass.
The present invention is directed to a new and improved multiple pole switch assembly for an inertial switch which embodies the following features: greater precision in the simultaneous actuation between individual sets of contacts; reliable actuation of the individual sets of contacts at relatively small actuating forces and relatively small amounts of inertial mass travel; ability to carry required current levels for required amounts of time; avoidance of adding excessive cost to existing supplemental inflatable restraint systems; ability to withstand and function in severe impact situations; maintenance of the independency of each individual set of contacts; and the ability to withstand reasonable levels of vibration. Insofar as the applicant is aware, there is no device currently available which possesses these capabilities, although multiple pole inertial switches are known.
The invention possesses the further advantage of comprising a relatively small number of component parts that have to be assembled together. Many of the features of the invention are embodied in the particular configurations of these individual parts and the relationships between the individual parts. By way of example, the presently preferred dual pole embodiment of switch assembly that will be illustrated and described, comprises seven parts; namely, a ball retainer, a contact support, an actuator disk, and two sets of contacts, each containing a first electrical contact element and a second electrical contact element.
Operational features arising from the disclosed embodiment include: contact travel that is an amplification of the actuator disk travel; the spacing of the contacts in each set and position of the disk in relation to the contacts both being preset by features of the contact support and actuator disc resulting in closer tolerance control over the operating characteristics to ensure that both circuits will be simultaneously signalled with a high degree of precision; and positive prevention of excessive overtravel of the actuator disc. The invention also affords the ability to provide unique calibrations for different models of inertial switches by simply changing the dimension of a portion of the actuator disc.
Further features, advantages and benefits of the invention will be seen in the ensuing descriptions and claims. Drawings accompany the disclosure and illustrate a preferred embodiment of the invention according to the best mode contemplated at the present time in carrying out the invention.